Process and an arrangement for the strenghtening of an end portion of a yarn

Abstract

For the strengthening of an end portion of a yarn which extends on a spinning station of a spinning machine between a stopped spool package and a suction withdrawal device assigned to the spinning station, the yarn which projects into the withdrawal device is gripped, is lengthened by the winding-off of the yarn wound onto the spool package, and is then strengthened in an essentially stationary position by means of a twisting entered in the area of the yarn end. In the case of an arrangement provided for this purpose, particularly mechanically operating twisting devices are used.

What is claimed is: 
     
       1. A process for strengthening of an end portion of a yarn which is produced at a spinning station of a spinning machine comprising a plurality of such spinning stations and which yarn, after the interruption of the spinning operation, extends between a stopped spool package and a suction withdrawal device assigned to the spinning station, said process comprising: gripping a yarn end projecting into the suction withdrawal device;   lengthening the yarn end portion by winding-off the yarn would up on the package; and   twisting the yarn end portion while it is in an essentially stationary position to thereby strengthen the yarn end portion by applying a true twist thereto.   
     
     
       2. A process according to claim 1, comprising holding the yarn end portion to be strengthened in a clamped position during the strengthening. 
     
     
       3. A process according to claim 2, wherein the twisting includes a mechanical non-pneumatic twisting of the yarn end portion situated between a clamping element and the package. 
     
     
       4. A process according to claim 3, comprising cutting off an end part of the yarn which is not to be strengthened. 
     
     
       5. A process according to claim 4, comprising controlling the length of the yarn end portion to be strengthened by controlling an application point of the twisting with respect to the stopped spool package. 
     
     
       6. A process according to claim 4, wherein said gripping includes gripping the yarn end projecting into the suction withdrawal device by means of a gripping element, wherein said lengthening includes sucking said yarn end together with a yarn portion wound off the spool package into a suction tube which is separate from the suction withdrawal device and is applied to the spinning station, wherein said strengthening is then applied in an area of the yarn end. 
     
     
       7. A process according to claim 3, comprising controlling the length of the yarn end portion to be strengthened by controlling an application point of the twisting with respect to the stopped spool package. 
     
     
       8. A process according to claim 3, wherein said gripping includes gripping the yarn end projecting into the suction withdrawal device by means of a gripping element, wherein said lengthening includes sucking said yarn end together with a yarn portion wound off the spool package into a suction tube which is separate from the suction withdrawal device and is applied to the spinning station, wherein said strengthening is then applied in an area of the yarn end. 
     
     
       9. A process according to claim 2, comprising cutting off an end part of the yarn which is not to be strengthened. 
     
     
       10. A process according to claim 2, comprising controlling the length of the yarn end portion to be strengthened by controlling an application point of the twisting with respect to the stopped spool package. 
     
     
       11. A process according to claim 1, comprising cutting off an end part of the yarn which is not to be strengthened. 
     
     
       12. A process according to claim 11, wherein said gripping includes gripping the yarn end projecting into the suction withdrawal device by means of a gripping element, wherein said lengthening includes sucking said yarn end together with a yarn portion wound off the spool package into a suction tube which is separate from the suction withdrawal device and is applied to the spinning station, wherein said strengthening is then applied in an area of the yarn end. 
     
     
       13. A process according to claim 1, comprising controlling the length of the yarn end portion to be strengthened by controlling an application point of the twisting with respect to the stopped spool package. 
     
     
       14. A process according to claim 13, wherein said gripping includes gripping the yarn end projecting into the suction withdrawal device by means of a gripping element, wherein said lengthening includes sucking said yarn end together with a yarn portion wound off the spool package into a suction tube which is separate from the suction withdrawal device and is applied to the spinning station, wherein said strengthening is then applied in an area of the yarn end. 
     
     
       15. A process according to claim 1, wherein said gripping includes gripping the yarn end projecting into the suction withdrawal device by means of a gripping element, wherein said lengthening includes sucking said yarn end together with a yarn portion wound off the spool package into a suction tube which is separate from the withdrawal device and is applied to the spinning station, wherein said strengthening is then applied in an area of the yarn end. 
     
     
       16. An arrangement for strengthening of an end portion of a yarn which is produced at a spinning station of a spinning machine comprising a plurality of such spinning stations and which, after the interruption of the spinning operation, extends between a stopped spool package and a suction withdrawal device assigned to the spinning station, said arrangement comprising: a suction withdrawal pipe which is connected downstream of the suction withdrawal device of the spinning station;   spool package drive uncoupling devices for uncoupling a drive of a spool package receiving the spun yarn;   a controllable gripping element selectively grippingly engageable with the yarn projecting into the withdrawal pipe;   guiding devices for guiding the yarn away from the withdrawal pipe; and   a twisting device for twisting the yarn end portion of the yarn which leads onto the spool package to thereby strengthen the yarn end portion by applying a true twist to said yarn end portion while it is in an essentially stationary position.   
     
     
       17. An arrangement according to claim 16, wherein the twisting device includes a clamping element for the yarn to be strengthened. 
     
     
       18. An arrangement according to claim 17, wherein the clamping element of the twisting device is constructed as a gripping element. 
     
     
       19. An arrangement according to claim 18, wherein the twisting device has a rotatably arranged, drivable slotted disk with a radially arranged slot which extends to the center and into which the yarn to be strengthened can be introduced and can be fixed by means of a yarn clamp arranged on the slotted disk. 
     
     
       20. An arrangement according to claim 19, wherein the slotted disk is rotatable by means of an assigned driving disk. 
     
     
       21. An arrangement according to claim 20, wherein the slotted disk and the driving disk are magnetically connected with one another. 
     
     
       22. An arrangement according to claim 20, wherein the slotted disk and the driving disks are each provided with an external toothing. 
     
     
       23. An arrangement according to claim 20, wherein the slotted disk can be driven by means of two magnetic driving disks which are applied to its circumference. 
     
     
       24. An arrangement according to claim 19, wherein the slotted disk is arranged between rims. 
     
     
       25. An arrangement according to claim 16, wherein the gripping element and the twisting device are assigned to a servicing arrangement which is arranged to be movable along the spinning machine to be selectively applied to the spinning stations. 
     
     
       26. An arrangement according to claim 25, wherein the gripping element and the twisting device are arranged on a swivel arm which can be jointly applied to the spinning stations. 
     
     
       27. An arrangement according to claim 25, wherein a suction tube is provided which can be applied to the withdrawal pipe and is assigned to the servicing arrangement, the suction tube being provided on its mouth opening facing away from the servicing arrangement with a yarn clamp serving as the controllable gripping element, and wherein the twisting device is located at an end of the suction tube opposite its mouth opening. 
     
     
       28. An arrangement according to claim 27, wherein the twisting device is constructed as a rotatably driven tube into which the yarn to be strengthened is introduced and to which a clamping element is assigned for clamping the yarn. 
     
     
       29. An arrangement according to claim 28, wherein two clamping devices are provided as the clamping element which can be introduced into an interior space of the rotatably driven tube and is brought to rest against one another to clamp the yarn therebetween. 
     
     
       30. An arrangement according to claim 29, wherein the clamping elements are constructed as wing-type double levers which are received in recesses of the rotatably driven tube which are situated opposite one another and are arranged in the recesses so that they is swivelled on pins in such a manner that, in each case, a shorter and a longer leg is formed on the double lever so that during the rotation of the tube centrifugal forces move the longer legs toward the outside and the shorter legs are moved toward the inside, the yarn introduced into the tube being clamped between the shorter legs. 
     
     
       31. An arrangement according to claim 30, wherein the rotatably driven tube has a rectangular cross-section in the area in which the double levers are arranged. 
     
     
       32. An arrangement according to claim 31, wherein the double levers completely fill out the recesses in their inoperative position. 
     
     
       33. An arrangement according to claim 30, wherein the double levers completely fill out the recesses in their inoperative position. 
     
     
       34. An arrangement according to claim 16, wherein a cutting device is assigned to the twisting device by means of which an end portion of the yarn which is not intended for strengthening is cut off.